Cooling apparatus

ABSTRACT

Disclosed is a cooling apparatus including: a heat receiving plate to which a plurality of heating elements are attached; a radiator plate to which a plurality of Peltier devices are attached; a thermal transport heat pipe that couples the heat receiving plate with the radiator plate; and a heat dissipating device being provided on an exothermic side of the Peltier devices; wherein the plurality of heating elements are arranged along a longitudinal direction of the thermal transport heat pipe, and the plurality of Peltier devices are arranged along the longitudinal direction of the thermal transport heat pipe, whereby, when using a plurality of Peltier devices, reducing power consumption thereof by equalizing each operation of the respective Peltier devices.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cooling apparatus for cooling heatingelements.

2. Description of the Related Art

A cooling system, such as natural air cooling, forced air cooling, watercooling, and ebullient cooling, is well known. In recent years, heatingelements that require temperature regulation, such as light emittingdevices, are widely used. For example, the following Patent Document 1proposes a semiconductor laser apparatus which is provided with acooling mechanism by combining a Peltier device with a heat pipe.

In such a cooling mechanism as described in Patent Document 1, powerconsumption tends to increase because the Peltier device has arelatively small thermoelectric conversion efficiency. Further, if anendothermic amount of the Peltier device is increased, it may fall intoa supercooled state, thereby resulting in dew condensation.

The related prior arts are listed as follows: Japanese Patent UnexaminedPublications (kokai) JP-5-167143A (1993), JP-2001-332806A, JP-11-121816A(1999), JP-5-312455A (1993), and International Patent PublicationWO2004/029532, and Japanese Utility Model Unexamined PublicationJP-61-194170U (1986).

SUMMARY OF THE INVENTION

An object of the present invention is to provide a cooling apparatuscapable of, when using a plurality of Peltier devices, reducing powerconsumption thereof by equalizing each operation of the respectivePeltier devices.

In order to achieve the above object, the cooling apparatus according toan embodiment of the present invention includes:

a heat receiving plate to which a plurality of heating elements areattached;

a radiator plate to which a plurality of Peltier devices are attached;

a thermal transport heat pipe that couples the heat receiving plate withthe radiator plate; and

a heat dissipating device being provided on an exothermic side of thePeltier devices;

wherein the plurality of heating elements are arranged along alongitudinal direction of the thermal transport heat pipe, and

the plurality of Peltier devices are arranged along the longitudinaldirection of the thermal transport heat pipe.

It is preferable that the heat dissipating device includes: a secondheat receiving plate in contact with the exothermic sides of the Peltierdevices; a radiating heat pipe coupled to the second heat receivingplate; and a radiating fin coupled to the radiating heat pipe.

It is preferable that a plurality of radiating heat pipes are arrangedat the same interval along a direction perpendicular to the longitudinaldirection of the thermal transport heat pipe.

It is preferable that the cooling apparatus further comprising: atemperature sensor located near a coupling portion between the heatdissipating device and the thermal transport heat pipe; a plurality ofdrive circuits for individually driving the respective Peltier devices;and a control circuit for individually controlling the respective drivecircuit based on an output from the temperature sensor.

It is preferable that a tip end of the thermal transport heat pipe isprotruded from the end face of the heat dissipating device.

It is preferable that the heat receiving plate and the radiator plateare coupled by a plurality of thermal transport heat pipes, and asmaller amount of liquid is sealed in the heat pipe which is located ata larger distance from the heating element attachment portion.

It is preferable that a wick that generates a capillary force is fixedto an inner surface of the thermal transport heat pipe.

It is preferable that the thermal transport heat pipe is bent in aU-shape, and both ends of the thermal transport heat pipe are thermallycoupled by another heat pipe.

It is preferable that the thermal transport heat pipe is bent in aU-shape, and the heat receiving plate and the radiator plate areintegrated into a single piece and disposed perpendicularly to eachother.

It is preferable that the heating element which is located at a portioncloser to the end of the thermal transport heat pipe generates a smalleramount of heat.

It is preferable that an electronic or optical device is located at aposition other than under a endothermic surface of the Peltier device ina vertical direction.

It is preferable that the heat receiving plate is provided with aheater.

According to an embodiment of the present invention, heat generated bythe plurality of heating elements is dissipated through the heatreceiving plate and the thermal transport heat pipes by the plurality ofPeltier devices. Therefore, operations of the Peltier devices can beequalized to collectively control the temperature. Further, a differencein temperature between an endothermic side and an exothermic side ofeach Peltier device can be decreased, thereby reducing power consumptionof the Peltier devices.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are a plan view and a front view, showing a coolingapparatus according to Embodiment 1 of the present invention;

FIGS. 2A and 2B are a front view and a side view, showing a coolingapparatus according to Embodiment 2 of the present invention;

FIGS. 3A and 3B are a plan view and a front view, showing a coolingapparatus according to Embodiment 3 of the present invention;

FIGS. 4A, 4B and 4C are a left side view, a front view and a right sideview, showing a cooling apparatus according to Embodiment 4 of thepresent invention;

FIGS. 5A and 5B are a plan view and a front view, showing a coolingapparatus according to Embodiment 5 of the present invention; and

FIG. 6 is a plan view showing a cooling apparatus according toEmbodiment 6 of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This application is based on an application No. 2010-16409 filed on Jan.28, 2010 in Japan, the disclosure of which is incorporated herein byreference.

Hereinafter, preferred embodiments will be described with reference todrawings.

Embodiment 1

FIGS. 1A and 1B are a plan view and a front view, showing a coolingapparatus according to Embodiment 1 of the present invention. Thiscooling apparatus includes a heat receiving plate 2, a radiator plate 4,thermal transport heat pipes 5, a plurality of Peltier devices 3 and aheat sink 6.

The heat receiving plate 2 is made of a material having favorablethermal conductivity, like a metallic material such as copper oraluminum. An upper surface of the heat receiving plate 2 has a flatshape, on which a plurality of heating elements 1 such as semiconductorlasers are mounted. FIG. 1 shows one example in which three heatingelements 1 are mounted, but the number of the heating elements 1 may betwo or four or more. A lower surface of the heat receiving plate 2 has ashape substantially conforming to a shape of each of the thermaltransport heat pipes 5, thereby ensuring favorable thermal coupling.

The thermal transport heat pipes 5 are constituted such that workingfluid is sealed within a metallic pipe, and provide a function ofeffectively transporting heat by means of evaporation of the workingfluid, traveling of vapor, condensation of the vapor, and reflux ofliquid due to a capillary force within the heat pipe. One end of each ofthe thermal transport heat pipes 5 is joined with the heat receivingplate 2, and the other end is coupled with the radiator plate 4, thusthe heat receiving plate 2 is thermally coupled with the radiator plate4, thereby efficiently transporting heat from the heat receiving plate 2to the radiator plate 4. FIG. 1 shows one example in which two thermaltransport heat pipes 5 are provided, but the number of the thermaltransport heat pipes 5 may be one or three or more.

The radiator plate 4 is made of a material having favorable thermalconductivity, like a metallic material such as copper or aluminum. Alower surface of the radiator plate 4 has a shape substantiallyconforming to a shape of each of the thermal transport heat pipes 5,thereby ensuring favorable thermal coupling. An upper surface of theradiator plate 4 has a flat shape, on which a plurality of Peltierdevices 3 are mounted. FIG. 1 shows one example in which three Peltierdevices are mounted, but the number of the Peltier devices 3 may be twoor four or more.

The Peltier devices 3 utilize the Peltier effect in which an endothermicor exothermic phenomenon can occur at a junction between a p-type and ann-type semiconductors according to the direction of a current flowingthrough the junction. The endothermic surfaces of the Peltier devices 3are in contact with the upper surface of the radiator plate 4. Theexothermic surface of the Peltier devices 3 are attached with the heatsink 6.

The heat sink 6 is made of a material having favorable thermalconductivity, like a metallic material such as copper or aluminum, andhas such a configuration that a number of radiating fins are providedupright on a base plate.

As to a temperature control circuit, the cooling apparatus furtherincludes a temperature sensor 7, a plurality of drive circuits 52 forindividually driving the respective Peltier devices 3, and a controlcircuit 51 for individually controlling the respective drive circuits 52based on an output from the temperature sensor 7.

Next, an operation of this cooling apparatus is described by way ofexample based on a laser television, i.e., a television that generatesvideo images using light from R/G/B (Red/Green/Blue) light emittingelements, as one application of the present invention. The three heatingelements 1 including an R element, a G element and a B element generateheat during emission of desired light as each element is energized. Theheat generated by each of the heating elements 1 is transferred to theheat receiving plate 2, and then transferred to one end of the thermaltransport heat pipes 5. The thermal transport heat pipes 5 canefficiently transport heat by circulation of working fluid sealedtherein. At this time, when the working fluid receives heat from theplurality of heating elements 1, there is the same pressure within theheat pipe at portions at which each of the heating elements 1 isattached, and the working fluid can receive heat and evaporate at thesame temperature and the vapor thus generated can move in a collectivemanner. Accordingly, each of attachment surfaces of the R element, the Gelement and the B element has a substantially even temperature.

On the other hand, since at a portion where each of the Peltier devices3 is attached the vapor is uniformly dispersed and condensed such thateach of inner wall surfaces within the heat pipes has the sametemperature through the intermediary of the radiator plate 4, each ofthe endothermic surfaces of the plurality of Peltier devices 3 canreceive a uniform amount of heat at an even temperature through theintermediary of the radiator plate 4. In this manner, each of thePeltier devices 3 can receive an averaged heat quantity, and cantransfer the thermal energy received from the endothermic surface to theheat sink 6 using the Peltier effect. At this time, the Peltier device 3has a lower temperature on the side of the radiator plate and a highertemperature on the side of heat sink. Therefore, the heat sink 6 has atemperature higher than that of the thermal transport heat pipes 5,resulting in more efficient heat dissipation due to larger difference oftemperature with respect to the ambient temperature. Further, thetemperature of each of the thermal transport heat pipes, thus thetemperature at the portion where the heating element is attached can becontrolled by varying power supply to the Peltier devices 3.

Further, the Peltier device 3 may have a higher temperature on the sideof the radiator plate and a lower temperature on the side of heat sinkby inverting the flowing direction of a current supplied to the Peltierdevices 3. In other words, when heating the radiator plate 4, the heatis transferred through the radiator plate 4 and the thermal transportheat pipes 5 to the attachment surfaces, temperature of each is thusincreased. Accordingly, each of the attachment surfaces of the R/G/Belements can be maintained at any constant temperature regardless of theambient temperature. For example, even when the ambient temperaturerises from −5° C. up to 45° C., each of the endothermic surfaces of thePeltier devices 3 can be maintained at a constant temperature of 30° C.In the case of laser televisions, in view of the longer life of theR/G/B elements and the reduction of Peltier power consumption, it ispreferable to maintain the temperature at each of the endothermicsurfaces of the Peltier devices 3 in a range of 20 to 35° C., morepreferably in a range of 25° C. to 30° C.

Thus, the heating elements 1 can be cooled by temperature regulation,and it is possible to obtain desired properties (e.g., optical output)of the heating elements 1 by controlling the heating elements 1 at adesired temperature. The temperature used for temperature regulation canbe measured using the temperature sensor 7 such as thermocouple,thermistor, or diode. A measuring position of the temperature sensor 7may be at any point from the heat receiving plate 2 to the heat sink 6,but preferably at the radiator plate 4, in particular, as shown in FIG.1, more preferably near a coupling portion between the radiator plate 4and the thermal transport heat pipe 5. Moreover, when coupling with theplurality of thermal transport heat pipes 5, it is preferable to locatethe sensor 7 near the intermediate of the adjacent heat pipes on theradiator plate 4.

In the cooling apparatus according to this embodiment, the thermaltransport heat pipes 5 are used for heat uniformizing elements, and theplurality of heating elements 1 are arranged linearly along thelongitudinal direction of the thermal transport heat pipes 5, and theplurality of Peltier devices 3 are arranged linearly along thelongitudinal direction of the thermal transport heat pipes 5.Accordingly, the heat transferred from the plurality of heating elements1 is transported in a collective manner, and uniformly exhausted to theplurality of Peltier devices 3. As a result, the heat receiving plate 2and the radiator plate 4 can be maintained at a uniform temperaturewithin the respective planes.

Further, even when the heat generated by each of the heating elements 1is not uniform, the heat can be uniformly transferred to each of thePeltier devices 3. Accordingly, the thermal transport efficiency of eachof the Peltier devices 3 can be maintained at a maximal state, in otherwords, the difference in temperature between the endothermic surface andthe exothermic surface of each Peltier device 3 can be maintained at auniform condition. As a result, it is possible to reduce the powerconsumption of the Peltier devices 3. Moreover, since the heat isuniformly transferred to each of the Peltier devices 3, localsupercooling can be prevented, thereby improving dew condensationresistance.

Further, in a case where each of the plurality of heating elements 1generates heat in a different mode (for example, one condition in whichR element: large, G element: small, B element: medium changes rapidly toanother condition in which R element: medium, G element: medium, Belement: small), compared to the case in which the Peltier device 3 isprovided for every heating element 1, each Peltier device can receiveheat of an average heat quantity out of the plurality of heatingelements 1. Accordingly, the variation of the generated heat quantitybecomes moderate, thereby facilitating the control of the temperature.In particular, when forming a video image of ocean (blue), for example,even when the R element: 0 (no load), the G element: 0 (no load), andthe B element: large, the R/G/B elements are provided for the same heatpipe, thereby preventing abnormally low temperature (0° C. when theambient temperature is 0° C.). Further, even when a particular heatingelement generates a larger mount of heat among the plurality of heatingelements 1, as long as the other heating elements generate a smallermount of heat, a total amount of heat exhausted is kept relativelysmall, thereby maintaining the particular heating element 1 at a lowertemperature.

Each of the R/G/B elements may change its coloring (wavelength) andlight intensity depending on the temperature of a luminescent body (LD)inside the element, and therefore it is preferable that the temperatureof the LD does not change too much in order to obtain desired light.However, each of the R/G/B elements has its unique thermal resistance,and the temperature of the LD element (junction temperature) may changeby the temperature difference obtained by integration of the generatedheat quantity that corresponds to the ever-changing light output forforming various video images (motion pictures). According to the presentinvention, since the attachment surface can be maintained at a constanttemperature as described above, the temperature of each of the LDelements can be more easily predicted and/or controlled only based oneach thermal resistance value that is a fixed value and generated heatquantity (supplied power) that represents transient change, withoutbeing affected by environment changes such as ambient temperature andsurrounding wind speed, which means high robustness. Further, abnormallylower temperature can be avoided even when any of the elements is underno load, and the temperature of the LD element varies only in a smallerrange, which defines a minimum temperature. Therefore it is possible toresume the temperature with favorable light emitting efficiency in thenext light output.

Incidentally, in the case of performing temperature regulationindividually for each of the R/G/B elements using the Peltier devices,1.5 or more Peltier devices are required in order to cool the R elementwith the adequately efficient number of the Peltier devices. In otherwords, in the individual cooling, the number of the Peltier devicesrequired for the R element is 1.5, the number of the Peltier devicesrequired for the G element is 2.3, and the number of the Peltier devicesrequired for the B element is 1.2. Consequently, the total number of therequired Peltier devices is seven, which is a physically possible totalnumber of 2, 3, and 2. However, by collectively cooling according to thepresent invention, all the elements can be satisfactory cooled with fivePeltier devices at a maximum output, and practically with four Peltierdevices due to interference of heat generation modes of individualelements, thereby decreasing the number of the Peltier devices andreducing the size, power consumption, and cost.

Embodiment 2

FIGS. 2A and 2B are a front view and a side view, showing a coolingapparatus according to Embodiment 2 of the present invention. Thiscooling apparatus has a configuration similar to that shown in FIG. 1,but is different in that each thermal transport heat pipe 5 is bent in aU-shape, and a heat receiving and radiating plate 8 is used in which theheat receiving plate 2 and the radiator plate 4 shown in FIG. 1 areintegrated into a single piece and disposed perpendicularly to eachother. With such a configuration, it is possible to realize downsizingof the entire apparatus. The temperature control circuit of the coolingapparatus has the same configuration as that shown in FIG. 1, andtherefore not shown in the drawing.

The thermal transport heat pipe 5 according to this embodiment can be acommon heat pipe including a circular pipe, a grooved pipe, a wire-linedpipe, or a particle sintered pipe. However, when bending the heat pipemore than one time, a problem may occur that a wick (such as thin wireor particle) that generates an inner capillary force is peeled off froman inner surface of the pipe. Further, when operating at a ultralowtemperature (40° C. or lower in the case of water), another problem mayoccur that a maximum amount of heat transport is reduced as viscositycoefficient of liquid increases. In such cases, it is preferable to usea heat pipe manufactured by lining a number of thin wires along an innerwall of a grooved pipe, followed by providing a ribbon for holding thethin wires from the inner side thereof, and then sintering it to fix thethin wires. By using a heat pipe of this type, the inner wick is hardlypeeled off even in deformation due to post processing such as bendingmore than once, and the maximum amount of heat transport can be improvedby ensuring a large flow path configured of grooves that facilitatereflux of high viscosity liquid.

Further, in the case of using the plurality of thermal transport heatpipes 5, a problem may occur that a difference in temperature between awall of the heat pipe and a liquid becomes smaller as a distance betweena heat pipe and the heating element attachment portion increases,resulting in an operational failure (for example, vapor does not easilytravel) and deterioration in the thermal transport property. In such acase, it is preferable to seal a smaller amount of liquid in the heatpipe which is located at a larger distance from the heating elementattachment portion. Thus, thickness of a liquid film formed on the innerwall of the heat pipe can be made smaller, and evaporation phenomenoncan easily occur even with a smaller difference in temperature. As aresult, it is possible to ensure thermal transport under normal vapor,thereby improving the maximum amount of heat transport and realizingthermal transport even with a smaller difference in temperature.

Moreover, a portion closer to the end of the thermal transport heat pipe5 that is in contact with the heat receiving plate 2 has a longer liquidreflux distance, with reflux properties of the liquid being lowered.Therefore, providing the heating element 1 that generates a largeramount of heat at the end of the heat pipe may cause occurrence of“dryout”, that is, no liquid is resupplied and the temperature at theattachment portion may rise up. In order to address this problem, amongthe plurality of heating elements 1 attached to the heat receiving plate2, a heating element that generates a smaller amount of heat ispreferably located at a portion closer to the end of the thermaltransport heat pipe. Consequently, an allowable limit value of a totalamount of exhaust heat quantity to be dissipated from the plurality ofheating elements 1, that is, the maximum amount of heat transport of theheat pipe is further increased.

In the case of the laser television, the G element is likely to generatethe largest amount of heat, therefore, the G element is preferablylocated at a position closest to the heat sink along the heat pipe.

Embodiment 3

FIGS. 3A and 3B are a plan view and a front view, showing a coolingapparatus according to Embodiment 3 of the present invention. Thiscooling apparatus includes the heat receiving plate 2, the radiatorplate 4, the thermal transport heat pipes 5, the plurality of Peltierdevices 3, and a heat dissipating unit 20. The cooling apparatus has aconfiguration similar to that shown in FIG. 1, but is different in thatthe heat dissipating unit 20 including radiating heat pipes 10 is usedin place of the heat sink 6 shown in FIG. 1. The temperature controlcircuit of the cooling apparatus has the same configuration as thatshown in FIG. 1, and therefore not shown in the drawing.

The heat dissipating unit 20 includes a second heat receiving plate 9 incontact with the exothermic side of each Peltier device 3, the pluralityof radiating heat pipes 10 coupled to the second heat receiving plate 9,and radiating fins 11 coupled to the respective radiating heat pipes 10.

The second heat receiving plate 9 is made of a material having favorablethermal conductivity, like a metallic material such as copper oraluminum. A lower surface of the second heat receiving plate 9 has aflat shape which is in contact with the exothermic side of the pluralityof Peltier devices 3. An upper surface of the second heat receivingplate 9 has a shape substantially conforming to a shape of each of theradiating heat pipes 10, thereby ensuring favorable thermal coupling.

The radiating heat pipe 10 is constituted similarly to the thermaltransport heat pipe 5, such that working fluid is sealed within ametallic pipe, and provides a function of effectively transporting heatby means of evaporation of the working fluid, traveling of vapor,condensation of the vapor, and reflux of liquid due to a capillary forcewithin the heat pipe. One end of each radiating heat pipe 10 is joinedwith the second heat receiving plate 9, and the other end is joined withthe radiating fins 11, thereby efficiently transporting heat from thesecond heat receiving plate 9 to the radiating fins 11. FIG. 3 shows oneexample in which six radiating heat pipes 10 are provided, but thenumber of the radiating heat pipes 10 may be one to five or seven ormore.

The radiating fin 11 is configured of a plurality of plates made of amaterial having favorable thermal conductivity, like a metallic materialsuch as copper or aluminum. The plates are arranged at substantially thesame interval along the longitudinal direction of the radiating heatpipe 10.

According to this embodiment, a heat dissipating capability isdramatically improved by using the heat dissipating unit 20 as describedabove. Further, it is preferable that the plurality of radiating heatpipes 10 are arranged at the same interval along a directionperpendicular to the longitudinal direction of the thermal transportheat pipe 5. Thus, in the case where the plurality of Peltier devices 3are provided, a larger number of heat dissipating heat pipes 5 can belocated as compared to the case where the thermal transport heat pipes 5and the radiating heat pipes 10 are parallelly located, thereby furtherimproving heat dissipating properties. Moreover, in the case of usingthe above-mentioned U-shaped heat pipe, it is preferable to place theheat pipe in a horizontal plane because the operation may bedeteriorated if the liquid sealed within the heat pipe accumulatesaround a U-shaped portion or both ends by gravity. In this case, theentire apparatus can be downsized by providing the heat dissipating unitincluding the perpendicular heat pipes.

The heat dissipating 20 is required to exhaust the total amount of heatincluding the heat quantity generated from the heating elements 1 andthe driving power of the Peltier devices 3, thus desired to exhaust agreater amount of heat and to have a larger value of maximum heattransport capability. Moreover, the further the heat dissipatingproperties of the heat dissipating unit 20 improves, the lower thetemperature of the exothermic surface of the Peltier device 3 becomes,and the smaller the difference in temperature between the endothermicsurface and the exothermic surface of the Peltier device 3 becomes.Accordingly, the power consumption of the Peltier devices 3 can bereduced to save energy.

Embodiment 4

FIGS. 4A, 4B and 4C are a left side view, a front view and a right sideview, showing a cooling apparatus according to Embodiment 4 of thepresent invention. This cooling apparatus has a configuration similar tothat shown in FIG. 2, but is different in that each thermal transportheat pipe 5 is bent in a U-shape, and the heat receiving and radiatingplate 8 is used in which the heat receiving plate 2 and the radiatorplate 4 shown in FIG. 1 are integrated into a single piece and disposedperpendicularly to each other. With such a configuration, it is possibleto realize downsizing of the entire apparatus. The temperature controlcircuit of the cooling apparatus has the same configuration as thatshown in FIG. 1, and therefore not shown in the drawing.

In this embodiment, a tip end 12 of the thermal transport heat pipes 5is protruded from the end face of the radiator plate 4. If there is aninitial residual non-condensable gas (e.g., nitrogen) or anon-condensable gas generated from residual metals (e.g., hydrogen)present within the heat pipe, the gas can be moved to remain at acondensation side end portion of the heat pipe during operation.Further, an excess of the liquid sealed within the heat pipe can be alsomoved to remain at the condensation side end portion. Accordingly, thevapor cannot enter the condensation side end portion of the heat pipe,at which the heat cannot be exchanged. If the Peltier devices areattached to this portion, which is then forcibly cooled, thiscondensation side end portion may have an abnormally lower temperaturewith respect to other condensation portions. Once dew condensationoccurs at the abnormally lower temperature portion, the condensed waterdroplets are possibly attached to electronic and optical components.

In contrast, when a tip end 12 of the thermal transport heat pipes 5 isprotruded from the end face of the radiator plate 4, a non-coolingportion can be formed at the tip end 12 of the thermal transport heatpipes 5, thereby ensuring a space that can accommodate thenon-condensable gas and the excessive liquid. As a result, theabove-mentioned problems, such as abnormally lower temperature and dewcondensation, can be solved.

Further, according to this embodiment, a bypass heat pipe 13 is providedin addition to the thermal transport heat pipes 5. One end of the heatpipe 13 is coupled to the vicinity of a coupling portion between theheat receiving plate 2 and one end of the thermal transport heat pipe 5.The other end of the heat pipe 13 is coupled to the vicinity of anothercoupling portion between the radiator plate 4 and the other end of thethermal transport heat pipe 5.

As described above, the condensation side end portion of the thermaltransport heat pipe 5 is likely to be supercooled by the Peltier devices3, causing dew condensation. As a countermeasure to this problem,providing the additional heat pipe 13 can make direct supply of heat toa portion to which heat is not easily transferred through vapor movementin the thermal transport heat pipe 5. As a result, dew condensationcaused by supercooling can be prevented.

Further, since an end portion on the heat receiving side of the thermaltransport heat pipe 5 has the longest distance for reflux of thecondensation liquid, and thus lower reflux capability of the liquid. Iftoo large a mount of heat is supplied to this end portion, the liquidinside the pipe is dried, thus causing “dryout”. Also in this case,providing the additional heat pipe 13 allows a part of the heat quantitysupplied from the heating elements 1 to be transferred in a bypassmanner via the heat pipe 13 to the radiator plate 4, thereby preventingthe dryout.

Moreover, according to this embodiment, in the case where the heatingelements 1, the heat receiving plate 2, and a control board 14 are to belocated from the above under gravity environment, as shown in FIG. 4A,it is preferable that the control board 14 is not positioned under thePeltier devices 3. Further, it is more preferable that the control board14 is positioned above the Peltier devices 3. In this arrangement, evenif any one of the Peltier devices 3 is supercooled to a lowesttemperature, causing dew condensation and fallen water droplets, thenthe water droplets can be prevented from attaching to the control board14, thereby surely preventing electrical and optical problems, such asshort circuit, contamination, etc.

Embodiment 5

FIGS. 5A and 5B are a plan view and a front view, showing a coolingapparatus according to Embodiment 5 of the present invention. Thiscooling apparatus has a configuration similar to that shown in FIG. 3,but is different in that the heat receiving plate 2 is provided with aheater 30. In this configuration, it is possible to perform temperatureregulation by energizing the heater 30 to heat the heat receiving plate2, even when the ambient temperature falls and the temperature of theentire apparatus also falls so that the heating elements 1 cannot have adesired temperature during heat generation. Incidentally, thetemperature of the attachment surface can be raised up by inverting thedirection of a current flowing through the Peltier devices 3 to raise upthe temperature of the radiator plate 4, but inverting the direction ofa current flowing through the Peltier devices 3 shifts the lowertemperature surface into the higher temperature surface, and vice versa,thereby causing large variation in temperature. Consequently, thematerial constituting the Peltier device 3 is likely to thermally expandand contract at a higher degree, resulting in fatigue breakdown.Therefore, providing such a heater as described above can achieve longerduration of life. In addition, directly heating the heat receiving plate2 can rapidly increase the temperature of the attachment surface of theR/G/B elements, thereby improving response of the temperatureregulation.

In the case of the laser television, at too low a temperature the R/G/Belements cannot generate adequate optical outputs due to theirproperties, but the R/G/B elements can generate adequate optical outputsaccording to this embodiment. Further, when turning on the televisionwhich has been kept at a lower temperature in a turning-off condition,the R/G/B elements having a lower temperature cannot generate opticaloutputs, thereby extending a latency time to wait for image formation.According to this embodiment, when the television is turned off,energizing the heater 30 can keep the R/G/B elements at a desiredtemperature, thereby reducing the latency time.

Further, when the heater 30 is provided, a power source for the Peltierdevices 3 or a power source for the heater 30 can alternately operate,hence, the power source can be shared to downsize the apparatus.

Embodiment 6

FIG. 6 is a plan view showing a cooling apparatus according toEmbodiment 6 of the present invention. This embodiment has aconfiguration similar to that shown in FIG. 3, but is different in thatthe plurality of heating elements 1 are arranged non-linearly along thelongitudinal direction of the thermal transport heat pipes 5, and theplurality of Peltier devices 3 are arranged non-linearly along thelongitudinal direction of the thermal transport heat pipes 5. Also withsuch a configuration, the heat transferred from the plurality of heatingelements 1 is transported in a collective manner, and uniformlyexhausted to the plurality of Peltier devices 3. As a result, the heatreceiving plate 2 and the radiator plate 4 can be maintained at auniform temperature within the respective planes.

Although the present invention has been fully described in connectionwith the preferred embodiments thereof and the accompanying drawings, itis to be noted that various changes and modifications are apparent tothose skilled in the art. Such changes and modifications are to beunderstood as included within the scope of the present invention asdefined by the appended claims unless they depart therefrom.

1. A cooling apparatus, comprising: a heat receiving plate to which aplurality of heating elements are attached; a radiator plate to which aplurality of Peltier devices are attached; a thermal transport heat pipethat couples the heat receiving plate with the radiator plate; and aheat dissipating device being provided on an exothermic side of thePeltier devices; wherein the plurality of heating elements are arrangedalong a longitudinal direction of the thermal transport heat pipe, andthe plurality of Peltier devices are arranged along the longitudinaldirection of the thermal transport heat pipe.
 2. The cooling apparatusaccording to claim 1, wherein the heat dissipating device includes: asecond heat receiving plate in contact with the exothermic sides of thePeltier devices; a radiating heat pipe coupled to the second heatreceiving plate; and a radiating fin coupled to the radiating heat pipe.3. The cooling apparatus according to claim 2, wherein a plurality ofradiating heat pipes are arranged at the same interval along a directionperpendicular to the longitudinal direction of the thermal transportheat pipe.
 4. The cooling apparatus according to claim 1, furthercomprising: a temperature sensor located near a coupling portion betweenthe heat dissipating device and the thermal transport heat pipe; aplurality of drive circuits for individually driving the respectivePeltier devices; and a control circuit for individually controlling therespective drive circuit based on an output from the temperature sensor.5. The cooling apparatus according to claim 1, wherein a tip end of thethermal transport heat pipe is protruded from the end face of the heatdissipating device.
 6. The cooling apparatus according to claim 1,wherein the heat receiving plate and the radiator plate are coupled by aplurality of thermal transport heat pipes, and a smaller amount ofliquid is sealed in the heat pipe which is located at a larger distancefrom the heating element attachment portion.
 7. The cooling apparatusaccording to claim 1, wherein a wick that generates a capillary force isfixed to an inner surface of the thermal transport heat pipe.
 8. Thecooling apparatus according to claim 1, wherein the thermal transportheat pipe is bent in a U-shape, and both ends of the thermal transportheat pipe are thermally coupled by another heat pipe.
 9. The coolingapparatus according to claim 1, wherein the thermal transport heat pipeis bent in a U-shape, and the heat receiving plate and the radiatorplate are integrated into a single piece and disposed perpendicularly toeach other.
 10. The cooling apparatus according to claim 1, wherein theheating element which is located at a portion closer to the end of thethermal transport heat pipe generates a smaller amount of heat.
 11. Thecooling apparatus according to claim 1, wherein an electronic or opticaldevice is located at a position other than under a endothermic surfaceof the Peltier device in a vertical direction.
 12. The cooling apparatusaccording to claim 1, wherein the heat receiving plate is provided witha heater.